• Journal of Welding and Joining
• /
• v.26 no.4
• /
• pp.55-60
• /
• 2008

Structural reliability of electrical panels installed in naval vessels is of critical importance from structural performance viewpoint. The panels may be exposed to vibration and fatigue loadings from internal and external sources and wave loading which cause fatigue cracking. In this study, common methods such as burr grinding and post weld heat treatment (PWHT), for the fatigue strength improvement of weldments are investigated. Burr grinding is carried out using a electric grinder in order to remove surface defects and improve the weld bead profile. And also PWHT is carried out for the purpose of removing residual. The effectiveness of the two post treatment methods is evaluated in terms of fatigue strength improvement of welded structures.

• Journal of the Korean Society for Heat Treatment
• /
• v.25 no.2
• /
• pp.85-89
• /
• 2012

Transparent conductive ZnO/Ag/ZnO (ZAZ) multilayer films were deposited by Radio frequency (RF) magnetron sputtering and direct current (DC) magnetron sputtering. The effects of post deposition vacuum annealing temperature on the structural, electrical and optical properties of the ZAZ multilayer films were investigated. The thickness of ZAZ films is kept constant at ZnO 50 nm/Ag 5nm/ZnO 45 nm, while the vacuum annealing temperatures were varied from 200 and $400^{\circ}C$, respectively. As-deposited ZAZ films exhibit a sheet resistance of $6.1{\Omega}/{\Box}$ and optical transmittance of 72.7%. By increasing annealing temperature to $200^{\circ}C$, the resistivity decreased to as low as $5.3{\Omega}/{\Box}$ and optical transmittance also increased to as high as 82.1%. Post-deposition annealing of ZAZ multilayer films lead to considerably lower electrical resistivity and higher optical transparency, simultaneously by increased crystallization of the films.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2001.05a
• /
• pp.821-826
• /
• 2001

This paper presents four types of strut-tie model design approaches of structural concrete through the anchorage zone design of a post-tensioned concrete I-beam. The differences and distinctive feature of each approach in terms of structural type of selected strut-tie model, external force acting on strut-tie model, effective strength of concrete strut, and strut-tie model design procedure are analyzed and compared. The outcomes of present study enable structural designers to understand the merits and demerits of each strut-tie model design approach, and thus to conduct reasonable and accurate design of structural concrete.

• Structural Engineering and Mechanics
• /
• v.60 no.5
• /
• pp.781-794
• /
• 2016

Due to its relatively good safety performance and aesthetic benefits, laminated glass (LG) is increasingly being used as load-carrying members in modern buildings. This paper presents an experimental study into one applicational scenario of structural LG subjected to in-plane bending. The aim of the study is to reveal the in-plane behaviors of the LG beams made up of multi-layered glass sheets. The LG specimens respectively consisted of two, three and four plies of glass, bonded together by two prominent adhesives. A total of 26 tests were carried out. From these tests, the structural behaviors in terms of flexural stiffness, load resistance and post-breakage strength were studied in detail, whilst considering the influence of interlayer type, cross-sectional interlayer percentage and presence of shear forces. Based on the test results, analytical suggestions were made, failure modes were identified, corresponding failure mechanisms were discussed, and a rational engineering model was proposed to predict the post-breakage strength of the LG beams. The results obtained are expected to provide useful information for academic and engineering professionals in the analysis and design of LG beams bending in-plane.

• Structural Engineering and Mechanics
• /
• v.87 no.3
• /
• pp.273-282
• /
• 2023

Concrete construction, one of the oldest building practices, is commonly used in all parts of the world. Concrete is the primary building material for both residential and commercial constructions. The challenge of protecting the buildings, hence nation, against the attack of terrorism has raised the importance to explore the understanding of building materials against the explosion. In this research, a security check-post (reinforced concrete frame filled with plain cement concrete) has been chosen to study the behavior of structural elements under blast loading. Eight nitroglycerines-based dynamite blasts with varying amounts of explosive charge, up to 17 kg weight has been carried out at various scale distances. Pressure and acceleration time history records are measured using blast measuring instruments. Security check post after being exposed by explosive loading are photographed to view cracking/failure patterns on the structural elements. It is noted that with the increase of quantity of explosive, the dimensions of spalling and crack patterns increase on the front panels. Simple empirical analyses are conducted using ConWep and other design manuals such as UFC 3-340-02 (2008) and AASTP-1 (2010) for the purpose of comparison of blast parameters with the experimental records. The results of experimental workings are also compared with earlier researchers to check the compatibility of developed equations. It is believed that the current study presents the simple and preliminary procedure for calculating the air blast and ground shock parameters on the structures exposed to blast explosion.

• Structural Engineering and Mechanics
• /
• v.51 no.6
• /
• pp.955-971
• /
• 2014

Large post-buckling behavior of Timoshenko beams subjected to non-follower axial compression loads are studied in this paper by using the total Lagrangian Timoshenko beam element approximation. Two types of support conditions for the beams are considered. In the case of beams subjected to compression loads, load rise causes compressible forces end therefore buckling and post-buckling phenomena occurs. It is known that post-buckling problems are geometrically nonlinear problems. The considered highly non-linear problem is solved considering full geometric non-linearity by using incremental displacement-based finite element method in conjunction with Newton-Raphson iteration method. There is no restriction on the magnitudes of deflections and rotations in contradistinction to von-Karman strain displacement relations of the beam. The beams considered in numerical examples are made of lower-Carbon Steel. In the study, the relationships between deflections, rotational angles, critical buckling loads, post-buckling configuration, Cauchy stress of the beams and load rising are illustrated in detail in post-buckling case.

• Structural Engineering and Mechanics
• /
• v.67 no.4
• /
• pp.337-346
• /
• 2018

The purpose of this study is to investigate thermal post-buckling analysis of a laminated composite beam subjected under uniform temperature rising with temperature dependent physical properties. The beam is pinned at both ends and immovable ends. Under temperature rising, thermal buckling and post-buckling phenomena occurs with immovable ends of the beam. In the nonlinear kinematic model of the post-buckling problem, total Lagrangian approach is used in conjunction with the Timoshenko beam theory. Also, material properties of the laminated composite beam are temperature dependent: that is the coefficients of the governing equations are not constant. In the solution of the nonlinear problem, incremental displacement-based finite element method is used with Newton-Raphson iteration method. The effects of the fibber orientation angles, the stacking sequence of laminates and temperature rising on the post-buckling deflections, configurations and critical buckling temperatures of the composite laminated beam are illustrated and discussed in the numerical results. Also, the differences between temperature dependent and independent physical properties are investigated for post-buckling responses of laminated composite beams.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.11a
• /
• pp.165-168
• /
• 2006

Carbon fiber reinforced polymer(CFRP) have superior mechanical and chemical properties in comparison with conventional materials. And post-tensioning method has been used for structural reinforcement of RC structures due to easy installation and good effect of resisting capacity of structures. But the higher cost of CFRP and the loss of prestressing force with time are considered the major problems to use it. In this study, CFRP Strips and external post tensioning for rehabilitation of old concrete structures were adapted and optimal combination of these methods is considered. A total of 17 concrete members were made and tested. The types and numbers of CFRP strips and post-tensioning types were selected as major test variables. From test results, it is shown that the concrete members that post tensioned and bonded CFRP strips has a pronounced effect on the strength and deformational behavior. This present study indicates that external temporally post tensioning can reduce the amount of CFRP strips required and the combination of temporally post tensioning and CFRP strips may meet the strength and ductility requirements of old structures.

• Journal of the Korea Concrete Institute
• /
• v.29 no.2
• /
• pp.217-223
• /
• 2017

This research was planned to evaluate the structural performance of post tensioned(PT) concrete member subjected to fire. Prime objective was to suggest some techniques to evaluate the performance of post tensioned concrete beam and slab exposed to high temperature through experiment. To accomplish this objective, the following two scopes have been proceeded to verify the strength reducing ratio of strands and find out the difference of resisting force at the PT concrete members exposed to high temperature through the fire test. The properties of prestressing steel(tendon) in PT concrete beam and slab under variable temperatures were reviewed. The test of this study was shown that stress relaxation occurred at high temperature, and some restoration of tensional force appeared as it got cooling down. The residual tension of the post tensioned beams at 4 hours after reaching the target temperature were 70% at $400^{\circ}C$, 10% at $600^{\circ}C$ and 2% at $800^{\circ}C$. The post tensioned slabs were 94% at $400^{\circ}C$, 84.5% at $600^{\circ}C$ and 62% at $800^{\circ}C$. The reason why the residual tension loss of the post tensioned slab was relatively small was considered to be that the slab was exposed just one side to high temperature and the strength of the strand was restored larger than that of beam. Also, it was confirmed that the post tensioned member inevitably experienced the loss of strength by fire damage, and restoration design of the member should be required to compensate for the value as much as lost strength.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2004.04a
• /
• pp.389-395
• /
• 2004

We consider the interface between the parallel distributed memory multifrontal solver and the finite element method. We give in detail the requirement and the data structure of parallel FEM interface which includes the element data and the node array. The full procedures of solving a large scale structural problem are assumed to have pre-post processors, of which algorithm is not considered in this paper. The main advantage of implementing the parallel FEM interface is shown up in the case that we use a distributed memory system with a large number of processors to solve a very large scale problem. The memory efficiency and the performance effect are examined by analyzing some examples on the Pegasus cluster system.